The following discussion of the prior art is intended to place the invention in an appropriate technical context and enable its advantages to be more fully appreciated. However, any references to prior art throughout this specification should not be construed as an express or implied admission that such art is widely known or is common general knowledge in the relevant field.
It is well known that one of the most important aspects in agriculture and crop cultivation is the effective management of weeds. Weeds compete aggressively for limited resources in terms of space, water, sunlight and nutrients. Consequently, the emergence of weeds has a marked adverse impact on crop yield and quality. Moreover, due to their relatively fast growth rates compared to crops, if weeds are not eliminated or effectively managed, particularly during the early stages after crop planting, they can quickly dominate entire fields and result in serious yield losses.
In an attempt to ameliorate this problem, various chemical herbicides have been developed. However, a number of associated problems and limitations have emerged including the cost of these agricultural chemicals and associated application equipment, short and longer-term environmental toxicity effects, human toxicity effects including in some cases carcinogenic effects, increased herbicide resistance and incompatibility with organic farming techniques.
In an attempt to avoid these problems, a variety of mechanical weeding devices and systems have been developed, which can be broadly categorised as:—                manual weeding implements and tools such as hoes;        mechanical weeding implements adapted for towing behind tractors or similar vehicles and utilising tines, hoes, brushes or blades to kill, remove or disrupt weeds; and        robotic systems using automated or semi-automated manipulators to remove or disrupt targeted weeds.        
Robotic systems offer potential benefits in terms of automation and hence reduced labour cost. However, to date such systems have been prone to significant disadvantages or shortcomings including one or more of: an inability to accurately and consistently discriminate between weeds and crops or other plants; lack of precise control over manipulators; an inability to trace complex trajectories and operate effectively outside highly ordered or structured environments; an inability to accurately target weeds in close proximity to crops or other obstacles; an inability to integrate effectively with a variety of vehicular or other operating platforms; excessive size; excessive power consumption; poor reliability; and/or excessive cost.
It is an object of the present invention to overcome or ameliorate one or more disadvantages of the prior art, or at least to provide a useful alternative.